Process of utilizing waste ferrous liquors.



ing. The usual practice is to start the operlite thawing,

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udded.- The specific gravity of-the liquor as rouge or pigment and to convert the rellllllllflhildlll l l5. UEldTElltLlEl, d'lEh, ULIFJE U- A. ltElllllll, AND JOESJEJPH MGFETRIJDGE, F VAN- TIEld-G'rlEtTliT, lflllllillllfill'lhll'hlilllfit, ddSTlErNUllltS T0 AMERICAN SHEET AND TIN PLATE timlllllf dl l'll, 015' TTTTSJEBURlIl-H, PENNSYLVANIA, all. CORPORATION 015 NEW JERSEY."

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To all whom it mag/ concern: I

lBe it known that we, Wmnrmu T dosnrn ll/TCFETRIDGE, citizens of the United fltates, residing at Vandergrift, county of Westmoreland, and State of Pemisylvania, have invented certain new and useful lim provements in Processes for Utilising i faste l errous Liquors, of which the following is a specification.

This invention relates to a process of treatspent pickle liquors for the purpose of regenerating. the liquors, and utilising the treated liquors for pickling steel or iron.

The process of pickling consists in removing scale, oxide and the like, from the surface of metallic articles, by subjecting the articles to. the action of an acid bath, capable of removing the surface defects, and for the purpose of improving the surface appear' ance or to prepare the articles for subsequent treatment, such as. tin plating or galvanization with a bath containing from 3 to 5 percent. of a free acid, such as sulfuric or hydrochloric acid Steel or iron articles are submerged in the bath, and as. the acid is neutralized, fresh .acid is periodically increases with each addition of acid and batchof iron treated, and when a strength of from 28. to degrees Eaum is reached the further addition of acid is stopped, and as far as practical the acid is neutralized. When sulfuric acid is used (as is usually the case) this concentrated bath consists prhicipally of ferrous sulfate and a varying per cent of free acid, and as a medium for pickling steel or iron has no further value and is lnnown to the trade as spent pickle liquor, a

lit is the object of our invention to re cover a portion of the iron in this liquor maining amount of ferrous sulfate into ric and basic ferric sulfate, which we use for pickling steel or iron. lit will be evident that in this way all the iron and all the acid value of the liquor are utilised By our method of utilising spent pickle liquors, when the process of pichling" is once started with sullicient acid. to pickle a given quantity ofsteel or iron, no further acid is specification of lletters Patent.

necessary, except what is required to com Patented drug, 25, lhlldi implication filed October fill, this. serial Ito. mt-i113.

pensate for the mechanical loss in operation. The iron that is combined as ferrous sulfate is used in our process as a means of conveying oxygen, and by a series of steps of oxidation and reduction, the acid is used over-and over forpickling steel or iron, although the acid is not isolated as commercial acid, but is mixed with ferric sulfate, which we find has not only a beneficial edect in overcoming defects peculiar to the acid pickling process, but accelerates pickling". The iron removed from the steel or iron during the pickling process is recovered during the regenerating process as ferric mild, and the quantity of ozrid of iron removed is equivalent to the dissolving power of the regenerated liquors.

According to prior methods of utilizing cial copperas was decomposed by heat to form ferric mild and sulfuric anhydrid was liberated. By other methods, the spent pickle liquors were concentrated to the crystallizing point, and by continuing the evaporation, ferrous liquor salts were obtained. These salts were decomposed by heat to form oXid of iron and sulfuric anhydrid the latter being used in making commercial sulfuric acid. lllfhen ferroussulfate is decomposed into ferric oxid and sulfuric anhydrid the end reaction follows:

2lFeS@u+U:l c, +2il O,.

ldefore complete decomposition takes place, a series of intermediate reactions take place as follows: When the temperature is very low, basic ferric sulfate is formed by the reaction on further heating, the basic ferric sulfate decomposes, forming" ferric OXlCl and ferric sulfate and sulfuric anhydrid is setfree, the reaction being i ld T increasine" the tem verature the ferric D p sulfate decomposes forming ferric card and sulfuric anhydrid as follows:

, liltl In our process we furnace the ferrous sulfate or ferrous liquor salts, at a temperature below dull red heat, with admission of air and constant'stirring of the mass, so that oxidation rapidly takes place, and basic ferric sulfate FegiMSQQ is formed. By discontinuing the heat at this point or removing the charge, we can retain in the furnaced product all the acid value originally contained in the ferrous salts. By digesting the basic ferric sulfate in water, we regenerate sulfuric acid for pickling iron or steel, according to the following reaction:

By decantation and filtratiom we remove the ferric oxid as rouge-or pigment, and use the filtrate to pickle steel or iron according to the following reaction:

The foregoing is the end reaction when all the ferric sulfate has been reduced to ferrous sulfate and the free acid neutralized. The ferric sulfate which is present prevents the absorption of hydrogen by the ironor steel which is being pickl'edand also prevents the action of galvanic couples ordinarilycaused by the action of-the various constituents of iron or steel; for example, it is well known that under ordinary circumstances there is a difierence in potential between the pearlite and ferrite of steel which causes the formation of a galvanic couple with consequent electrolytic action. reason of the results which have just been described, the ferric sulfate acts as a depolarizer and the hydrogen which would under ordinary circumstances be obsorbed by the iron or steel is used to reduce the ferric to ferrous sulfate. -This depolarizing effect continuesuntil all the ferric sulfate has been reduced to ferrous sulfate. When the pickling operation is continued after all the ferric sulfate has been reduced, we no longer have the depolarizing effect, but the free sulfuric acid acts: directly on producing ferrous sulfate.

When the ferric sulfate has beenin part reduced, we prefer to re lenish the'bath with fresh ferric sulfate mixed with forrous sulfate), or with basic ferric sulfate, these salts being produced by the process above described. in the presence of water thebasic ferric sulfate breaks up into ferric oxid, ferric sulfate and sulfuric acid. In tgis way-we have'the depolarizing effect of t e pickling process, and when the specific gravity of the liquor reaches 30 to de grees Baum the liquor is drawn on and treated by our above described process,

It is well known that in the regular acid pickling process certain effects are produced iaoaee' the steel,

ferric sulfate 'throughhut the entire that cause permanent defects in the steel or iron treated. It IS also known that galvanic couples are formed simultaneously with the immersion of the steel or iron articles in the acid bath, the electrolytic hydrogen having a tendency to produce sponge at V the cathode of the couple, and by absorption of hydrogen, the steel or iron articles are affected in a manner that causes defects in the subsequent treatment of the steel, such as tin plating and galvanizing. By using our process the cause of these defects can be overcome and the defects prevented by accomplishing the pickling in presence of dopolarizing salts, such as ferric sulfate or ferric chlori-d. Moreover, the presence of ferric salts will produce a uniform crystalline surface on the articles treated.

Having thus described our invention in general terms, we will now describe the various steps a detail: lst Wa-ste ferrous sulfate liq s are heated and treated with fine oXid of iron in quantities equivalent to the free acid prescut, for the purpose of neutralizing the free acid and forming ferric sulfate. The treatment with ferric oxid can be accomplished in any suitable container.

2nd, The liquors are concentrated-in any or the well known apparatus for concen trating corrosive liquors, and evaporation of water continued to point of saturation. W hen the liquor has reached the point of saturation, the temperature and specific gravity of the liquor are such that the free acid dissolves the oXid of iron added in the first step of the process to form ferric sulfate. By continuinglxthe evaporation, ferric sulfate and ferrous sulfate are salted out.

3rd. The mimure of ferric sulfate and ferrous sulfate as produced inthe second step of the process is furnaced in any suitable furnace at a temperature below dull red heat, with admission of air and constant stirring of the salt, oxidizing the ferrous sulfate into basic ferric sulfate according to The ferric salt contained in the mixture being treated remains unchanged at the temperature stated, so that the product of this third step of the process is a mixture of ferric sul ate and basic ferric sulfate.

4th. The product of the third step of the process is digested in water in any suitable apparatus, the ferric sulfate dissolving and the basic ferric sulfate combining with water to form ferric oxid, ferric sulfate and sulfuric acid according to the reaction erego(so, ,+n o= I 2 a l 2 a) sl y 5th. The insoluble ferric oaid produced in the fourth step of the process is removed lti ran

from the solution by decantation and filtration by any of the well known apparatus used for that purpose, and the ferric orrid is washed to free 1t from soluble iron salts. The ferric ozrid is used to produce pigment. 6th. The filtrate of the fifth. step, consist mg of a mixture of ferric sulfate and free acid, is utilized for pickling steel or iron, which can be accomplished in any suitable apparatus. The strength of the liquor can vary to suit the requirements of the articles being treated. W e find that a solution containing from 2 to 5 per cent. free acid is well adapted to ordinary worlr. The pickling can be accelerated by raising the temperature; the temperature we have found most suited for usual work is from 130 to 150 degrees Fahrenheit. add steel or iron articles, which are rapidly pickled according to the reaction The hydrogen set free reduces the ferric sulfate to ferrous sulfate, according to the reaction The bath is replenished from time to time with ferric sulfate, which may be a mixture of ferric sulfate and ferrous sulfate as produced in the second step of the process, or by the mixture of ferric sulfate and free acid as produced in the fifth step. When the strength of the liquor has increased to to 35 degrees Baum, the addition of ferric sulfate is stopped, and the pickling operation continued until ferric salts are reduced to ferrous salts.

7th. When it is desirable to utilize the free acid contained in the spent liquor from the sixth step of the process, the pickling operation may continue until the free acid is neutralized by the reaction It will be apparent to those skilled in the art that considerable change could be made in the details of the process which we have described without departing from the spirit or scope of our invention.

What we claim is:

l. The process of utilizing spent ferrous liquor, which consists in oxidizing the ferrolls to ferric salts, and adding said ferric salts to an acid cleanin solution, whereby polarization is prevente in the presence of a metal to be cleaned, substantially as described.

2. The process of utilizing spent ferrous liquor, which consists in neutralizing the free acid in said liquor, oxidizing the ferrous To this bath we to ferric salts, and adding said feiric salts to an acid cleaning solution, whereby polarization is prevented in the presence of a metal to be cleaned, substantially described.

3. The process, of utilizing spent ferrous liquor inch consists in treating the liquor with .c rric crud to neutralize the free acid with theforinaticn of a ferric salt, oxidizing the ferrous to ferric salts, and adding sai ferric salts to an. acid cleaning solution, whereby polarization is prevented in the presence of a metal to be cleaned, substantially as described.

l. The process of utilizing spent ferrous liquor, which consists in neutralizing the free acid of said liquor, furnacing to oxidize the ferrous to ferric salts, digesting with water to dissolve thesoluble salts, and add ing said solution to an acid cleaning solution, whereby in the presence of a metal to be cleaned polarization is prevented, substantially as described.

5. The process of utilizing spent ferrous liquor, which consists in neutralizing the the ferrous to ferric salts, digesting with Water to dissolve the soluble salts, filtering salts, and adding the filtrate to an acid cleansolution, whereby in the presence of a metal to be cleaned the ferric salts are reduced to ferrous salts and polarization is prevented, substantially as described:

6. The process of utilizing spent ferrous sulfate liquor, whith consists in neutralizing the free acid in said liquor, evaporating said liquor, whereby the dissolved salts are separated out, oxidizing said salts to form ferric sulfate and adding said ferric sulfate to an acid sulfate cleaning liquor, whereby in the presence of iron said ferric sulfate is reduced to ferrous sulfate and polarization is prevented, substantially as described.

7. The process of utilizing spent ferrous sulfate liquor, which consists in neutralizing liquor, whereby the dissolved salts are separated out, oxidizing said salts to form ferric sulfate, treating said salts with water, filtering to separate ()Xld of iron from the soluble ferric sulfate, and adding said filtrate to an acid sulfate cleaning liquor, whereby in the presence of iron said ferric sulfate is reduced to ferrous sulfate and polarization is vented, substantially as described.

WILLIAM f. @EEiTERLlE, JR. CLIFFORD A. BEALE. JUSEPH MCFETRTDGFE. Witnesses:

SAMUEL K. HUNGER, JOHN W. finance.

to separate the soluble from the insoluble prefree acid of said liquor, furnacing to oxidize lllti the free acid in said liquor, evaporating said 

